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[October 16 AFP] the freshwater fish pirarucu (scientific name: Arapaima gigas) of the world’s largest class which inhabits a South American Amazon (Amazon) river, The paper that “armor” with the multilayer structure which was excellent in order to protect oneself from a voracious piranha has been evolved was published in English Science journal Nature Communications (Nature Communications) on the 15th.
The research team led by Mr. Robert Ritchie (Robert Ritchie) of ? U.S. University of California at Berkeley (University of California at Berkeley), By microscope investigation and mechanical testing, the scales of pirarucu have a very strong outer shell, and it discovered that it was a mechanism in which the pierced tooth breaks.
? scales are carrying out wave-like form, and divert pressure to the collagen layer which is downward and whose elasticity it is thick and is high.
It has multilayer structure called the “lamella” which twisted and overlapped, and this collagen itself has a thickness of about 50 nm (1 nm = 1/1 billion meter).
The lamellar structure can make the wide range distribute the pressure by reacting for “biting” and sideslipping for a while.
A paper will be pointed out if the scales of ? pirarucu are “remarkable examples of the evolution which the living thing origin substance achieved in order to realize a specific function.”
It says, “It receives that especially a piranha bites, and it is in order to oppose by defense of a multiplex level.”
? pirarucu is a huge carnivorous fish, the length grows up into a maximum of 4 meters, and weight grows up into 200 km or more.
The greatest threat for pirarucu is man, and the overhunting for edible will start in the 19th century, and it is apprehensive about extinction now.